diff --git a/pkgs/servers/mail/opensmtpd/default.nix b/pkgs/servers/mail/opensmtpd/default.nix
index 7174b45a6f77..76b247cfd841 100644
--- a/pkgs/servers/mail/opensmtpd/default.nix
+++ b/pkgs/servers/mail/opensmtpd/default.nix
@@ -4,14 +4,14 @@
 
 stdenv.mkDerivation rec {
   pname = "opensmtpd";
-  version = "6.6.3p1";
+  version = "6.6.4p1";
 
   nativeBuildInputs = [ autoconf automake libtool bison ];
   buildInputs = [ libasr libevent zlib libressl db pam ];
 
   src = fetchurl {
     url = "https://www.opensmtpd.org/archives/${pname}-${version}.tar.gz";
-    sha256 = "1dqysjlyl0x3qzdzc9sjrla0063vpmlyq735lzf88p7wgzmw1xwy";
+    sha256 = "1kyph9ycq0j21dl9n1sq5fns9p4gckdi0fmnf8awrcwrdcm9dyg2";
   };
 
   patches = [